Amazing 'pulse of darkness' ray tech birthed in US gov labs

IT use: Turns itself off then on again very quickly

US government boffins say they have invented a fiendishly cunning new kind of laser running on quantum dots which, rather than producing pulses of light, actually emits pulses of intense darkness.

Unsurprisingly but mildly sinisterly, the new invention has been dubbed the "dark pulse laser". It works using extremely clever quantum dots which unlike regular boring quantum dots are made out of "nanostructured semiconductor materials" grown in special US government labs.

"Quantum dots are known for unusual behaviour," according to a statement issued by the labs in question.

When electricity is put into these dots, the nano cunningness causes them all to behave like individual atoms and thus they all emit light at the same frequency in time with each other - hence it is coherent laser light.

But that's not the clever part. The clever part is this:

The new laser depends on the qdots' unusual energy dynamics, which have the effect of stabilizing dark pulses. After emitting light, qdots recover energy from within rapidly (in about 1 picosecond) but more slowly (in about 200 picoseconds) from energy inputs originating outside the qdots in the laser cavity. This creates a progression of overall energy gains gradually giving way to overall energy losses. Eventually, the laser reaches a steady state of repeated brief intensity dips—a drop of about 70 percent—from the continuous light background.

Thus the laser, brilliantly, is able to almost turn itself off and go dark. In itself this would be rather unimpressive, but the dark pulse laser goes briefly dark and then comes back on in just 90 picoseconds. As the dark-pulse can be measured, the laser is thus a means of measuring time very precisely.

The boffins of the US National Institute of Standards and Technology, who unlocked the secrets of darkness, are chuffed as ninepence with their new kit. They consider that it could be handy in the next generation of optical atomic ultraclocks and/or superpowered networking and comms kit of the future.

Full details are published in the journal Optics Express, under the title Dark pulse quantum dot diode laser. The lead boffin of the push was Mingming Feng. ®